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  <section id="cmake-osx-sysroot">
<span id="variable:CMAKE_OSX_SYSROOT"></span><h1>CMAKE_OSX_SYSROOT<a class="headerlink" href="#cmake-osx-sysroot" title="Link to this heading">¶</a></h1>
<p>Specify the location or name of the macOS platform SDK to be used.</p>
<p>If not set explicitly, the value is initialized by the <code class="docutils literal notranslate"><span class="pre">SDKROOT</span></code>
environment variable, if set.  Otherwise, the value defaults to empty,
and the compiler is expected to choose a default macOS SDK on its own.</p>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 4.0: </span>The default is now empty.  Previously a default was computed based on
the <span class="target" id="index-0-variable:CMAKE_OSX_DEPLOYMENT_TARGET"></span><a class="reference internal" href="CMAKE_OSX_DEPLOYMENT_TARGET.html#variable:CMAKE_OSX_DEPLOYMENT_TARGET" title="CMAKE_OSX_DEPLOYMENT_TARGET"><code class="xref cmake cmake-variable docutils literal notranslate"><span class="pre">CMAKE_OSX_DEPLOYMENT_TARGET</span></code></a> or the host platform.</p>
</div>
<p>In order to pass an explicit macOS SDK via the compiler's <code class="docutils literal notranslate"><span class="pre">-isysroot</span></code> flag,
users may configure their build tree with <code class="docutils literal notranslate"><span class="pre">-DCMAKE_OSX_SYSROOT=macosx</span></code>,
or <code class="docutils literal notranslate"><span class="pre">export</span> <span class="pre">SDKROOT=&quot;$(xcrun</span> <span class="pre">--sdk</span> <span class="pre">macosx</span> <span class="pre">--show-sdk-path)&quot;</span></code> in their
environment.</p>
<p>Notes:</p>
<ul class="simple">
<li><p>macOS compilers in <code class="docutils literal notranslate"><span class="pre">/usr/bin</span></code>, when not invoked with <code class="docutils literal notranslate"><span class="pre">-isysroot</span></code>,
search for headers in <code class="docutils literal notranslate"><span class="pre">/usr/local/include</span></code> before system SDK paths,
matching the convention on many platforms.  Users on macOS-x86_64 hosts
with Homebrew installed in <code class="docutils literal notranslate"><span class="pre">/usr/local</span></code> should pass an explicit SDK,
as described above, when not building with Homebrew tools.</p></li>
<li><p>Some Clang compilers have no default macOS SDK selection.  For these,
if <span class="target" id="index-0-variable:CMAKE_OSX_SYSROOT"></span><a class="reference internal" href="#variable:CMAKE_OSX_SYSROOT" title="CMAKE_OSX_SYSROOT"><code class="xref cmake cmake-variable docutils literal notranslate"><span class="pre">CMAKE_OSX_SYSROOT</span></code></a> is empty, CMake will automatically pass
<code class="docutils literal notranslate"><span class="pre">-isysroot</span></code> with the macOS SDK printed by <code class="docutils literal notranslate"><span class="pre">xcrun</span> <span class="pre">--show-sdk-path</span></code>.</p></li>
</ul>
<p>The value of this variable should be set prior to the first
<span class="target" id="index-0-command:project"></span><a class="reference internal" href="../command/project.html#command:project" title="project"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">project()</span></code></a> or <span class="target" id="index-0-command:enable_language"></span><a class="reference internal" href="../command/enable_language.html#command:enable_language" title="enable_language"><code class="xref cmake cmake-command docutils literal notranslate"><span class="pre">enable_language()</span></code></a> command invocation
because it may influence configuration of the toolchain and flags.
It is intended to be set locally by the user creating a build tree.
This variable should be set as a <code class="docutils literal notranslate"><span class="pre">CACHE</span></code> entry (or else CMake may
remove it while initializing a cache entry of the same name) unless
policy <span class="target" id="index-0-policy:CMP0126"></span><a class="reference internal" href="../policy/CMP0126.html#policy:CMP0126" title="CMP0126"><code class="xref cmake cmake-policy docutils literal notranslate"><span class="pre">CMP0126</span></code></a> is set to <code class="docutils literal notranslate"><span class="pre">NEW</span></code>.</p>
<p>Despite the <code class="docutils literal notranslate"><span class="pre">OSX</span></code> part in the variable name(s) they apply also to
other SDKs than macOS like iOS, tvOS, visionOS, or watchOS.</p>
<p>This variable is ignored on platforms other than Apple.</p>
</section>


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